Internal Threading a blind hole with a threaded chuck?

[tmenyc]

For some months, I wrote with numerous issues about threading on my Logan 820. Did a fair amount of restoring the machine, with help replaced the halfnuts, and now it's working like a charm; I've been regularly turning 48tpi with no issues.
Now I'm on to more subtle stuff. The title names it: My Logan has a screw-on chuck and does not have a hard stop. I'm internal threading, on soft material, mostly ebonite and acrylic, always close to the chuck. When close to the chuck I usually use a Beall collet chuck and ER32. The threading works wonderfully on a through hole but I can't figure out how best to do it in a blind hole. With thanks to all the Youtube video creators and the answers I could find here, the only one I saw that did NOT say "don't do this if you have a threaded chuck" was Tom Griffin, of Tom's Techniques. Tom's method is to turn the compound around to 30 degrees from pointing away, then working forward. It seems to make sense, except for measuring a 5 thou cut from a dial across the ways, which in my setup is really clunky.
Does this method make sense to those with far more experience?

Many thanks,
Tim

 

[mmcmdl]

You can thread out on the rear side .

 

[pontiac428]

.

 

[RJSakowski]

You can thread out on the rear side .

You still have to reverse the spindle to thread out. If you run the spindle in the forward direction, in order to thread out, you have to reverse the direction of the lead screw which means you would cut a left hand thread.

 

[WobblyHand]

Made my ER40 chuck back plate on a threaded spindle, threading going outwards, like this. Used a left handed threading tool.

The thread.

And done.

Threading outwards removed the pucker factor.

A stock G0602/G0752Z has no idler gear to reverse the lead screw. It always cuts a right hand thread. Lathe was in reverse. Thread cut is right handed. It wouldn't screw on my spindle if left handed!

My ELS can cut RH or LH screws, either forward or reverse.

 

[mmcmdl]

And as wobbly said , the threaded chuck is usually not an issue , just make sure it is locked tight . These top notch inserts may be going soon , too much to follow . 36 my be on the auction block .

 

[Firstram]

Just redesign everything and use left handed threads!

 

[Parlo]

You can thread out on the rear side .

Not safe for right hand threads with a threaded chuck.

 

[WobblyHand]

Not for right hand threads.

Incorrect, at least for my lathe, and perhaps for some others.

Put lathe in reverse and thread outwards. You get right hand threads. You need to use a LH tool. That is what I did, and the lathe cuts RH threads in reverse.

This assumes the spindle and lead screw are geared in sync AND no idler gear is inserted to reverse the sense of the lead screw.

The G0602 and G0752Z lathe do not come with an idler gear to cut LH threads. It is incapable of cutting LH threads due to its design. It cuts RH threads going in, and RH threads going out. Of course to cut the RH threads going out, the spindle must be reversed and the cutter put on the far side.

 

[pontiac428]

He's concerned about the chuck coming off of the threaded spindle in reverse. It's a legitimate concern, but probably not a real-world issue, it takes a bit of a whack to break the chuck loose from the spindle nose compared to the lighter loads from cutting a single point thread.